Major depression is often associated with hypersecretion of cortisol. Depressed patients also have a reduction in the number of glucocorticoid receptors (GR) in circulating lymphocytes. However, the relationship between GR in the brain and pituitary to GR located in peripheral lymphoid tissues has not be systematically investigated. The proposed studies will initially characterize the GR in brain (hypothalamus, hippocampus, frontal cortex), pituitary and lymphoid (thymus, spleen) tissues of rats in regards to the maximum number of GR, the dissociation constant of the GR, the degree of GR activation, the molecular weight of the GR and the specificity of the GR. The regulation of the GR will next be assessed in a stress-induced animal model of depression. Non-glucocorticoid mediation of GR changes will be assessed by stressing adrenalectomized rats. These studies will provide information on the regulation of the GR in brain and pituitary in an animal model of depression and its relationship and its relationship to GR regulation in peripheral lymphoid tissues. A GR assay procedure will be developed so that quantitative GR measurements can be performed using adrenal-intact rats. These studies will also allow the Principal Investigator to learn new techniques such as affinity labelling of steroid hormone receptors and DNA cellulose binding assays. Long-term goals resulting from these studies include application of molecular biology techniques to study the neurobiology of the GR as well as regulation of brain GR by antidepressant drugs. In addition, the techniques developed to examine GR regulation in rat brain will be extended to study human brain GR in disease states such as suicide and Alzheimer's disease, where abnormalities in cortisol regulation occur. These results of the proposed studies will help delineate the role of GR abnormalities in depression.